JPH052821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel system for a gas turbine engine, and more particularly to the supply of fuel to a fuel servo.

The fuel system of a gas turbine engine includes a low pressure pump that supplies low pressure fuel to a high pressure pump, and a high pressure pump that supplies high pressure fuel to a fuel spill valve, a fuel flow regulator, and a fuel servo. A fuel flow regulator supplies fuel to the burner manifold and associated fuel burners. Fuel servos use fuel to drive engine traps and other devices, such as variable stator vanes. The fuel spill valve returns fuel in excess of the required amount to the upstream low pressure side of the high pressure pump.

Many of these high-pressure pumps for fuel systems are gear pumps and must be of the appropriate size.
If this pump is too large, the fuel flow through the high pressure pump will gradually outweigh the fuel required by the engine, especially at slow engine speeds. This results in a large amount of fuel reflux from the fuel spill valve upstream of the high pressure pump, which increases the fuel temperature. It is important not to oversize the high pressure pump to reduce fuel circulation and temperature rise during slow speed conditions.

Accordingly, a device is provided for supplying low pressure fuel to a high pressure pump, the high pressure pump being adapted to supply high pressure fuel to a fuel flow regulator and a fuel spill valve, the fuel flow regulator supplying high pressure fuel to at least one fuel burner. the manifold and associated fuel burners, the fuel spill valve is adapted to return excess fuel to a low pressure side upstream of the high pressure pump, and the at least one fuel servo supplies high pressure fuel from a location downstream of the high pressure pump. The control device detects when the surplus fuel flow rate from the fuel spill valve to the upstream low pressure side of the high pressure pump reaches a predetermined value, and supplies at least one high pressure fuel when the surplus fuel flow rate is greater than the predetermined value. The present invention provides a fuel system for a gas turbine engine that is adapted to supply a fuel servo for a gas turbine engine.

The control device can include a fuel servo isolation valve having a piston disposed within the first cylinder and defining with the first cylinder a first chamber and a second chamber, the second chamber having a A spring acting on the piston is disposed therein, the end of the piston remote from the second chamber extending through the window of the first cylinder and the window of the second cylinder, the second cylinder extending through the window of the third cylinder.
the first chamber is connected to the low pressure side of the high pressure pump and the fuel spill valve, the second chamber is connected to a relatively low fuel pressure point in the fuel system, and the third chamber is connected to the low pressure side of the high pressure pump and the fuel spill valve; the spring is adapted to control high pressure fuel flow to the at least one fuel servo, and when actuated, the spring biases the end of the piston remote from the second chamber to control high pressure fuel flow to the at least one fuel servo The piston is movable from a first position to a position where the end of the piston distal to the second chamber moves out of the third chamber to permit high pressure fuel flow to the at least one fuel servo. A predetermined pressure drop is created across the piston, and when the predetermined pressure drop overcomes the spring, the piston moves against the spring.

The control device can include a fuel servo isolation valve having a piston disposed within the cylinder and defining with the cylinder a first chamber, a second chamber and a third chamber, the second chamber being connected to the piston. disposed therein a spring acting on the piston, the end of the piston remote from the second chamber being biased by the spring into the third chamber;
The first chamber is connected to the low pressure side of the high pressure pump and the fuel spill valve, the second chamber is connected to a point in the fuel system where the fuel pressure is relatively low, and the third chamber is connected to the low pressure side of the high pressure pump and to the fuel spill valve;
and a spring biases the end of the piston distal from the second chamber to control high pressure fuel flow to the at least one fuel servo when actuated. The piston is movable from a first position where the end of the piston distal to the second chamber moves out of the third chamber to permit high pressure fuel flow to the at least one fuel servo. , a predetermined pressure drop is created across the piston, and the piston moves against the spring when the predetermined pressure drop overcomes the spring.

The control device can include a check valve having a piston disposed within the cylinder and defining with the cylinder a first chamber and a second chamber, the second chamber biasing the piston against the valve seat. the piston has a predetermined size window connecting the first chamber and the second chamber, the first chamber being connected to the first chamber of the fuel spill valve and the fuel servo isolation valve; is,
the second chamber is connected to a point in the fuel system where the fuel pressure is relatively low and the second chamber of the fuel servo shutoff valve, the point in the fuel system where the fuel pressure is relatively low is upstream of the high pressure pump on the low pressure side; In operation, excess fuel flow from the fuel spill valve to the upstream low pressure side of the high pressure pump flows through the first chamber of the check valve, the piston window and the second chamber, where the piston window having a predetermined size to produce a predetermined pressure drop across the check valve when a predetermined value is reached, and the predetermined pressure drop across the check valve is caused by moving a piston in the fuel servo isolation valve to generate at least one to allow high pressure fuel to be supplied to the fuel servo.

The fuel flow regulator is capable of supplying high pressure fuel to the at least one fuel servo via the third chamber of the fuel servo isolation valve.

A spring in the second chamber of the check valve is selected to move a piston in the check valve away from the valve seat to limit pressure buildup in the first chamber of the check valve.

When the engine is operating at high speed, even if the surplus fuel flow from the fuel spill valve to the upstream low-pressure side of the high-pressure pump falls below the predetermined value, at least 1
The area of the piston end remote from the second chamber of the fuel servo isolation valve is selected such that the pressure of the high pressure fuel is large enough to maintain high pressure fuel flow to the two fuel servos. The control device can include a check valve having a piston disposed within the cylinder and defining with the cylinder a first chamber and a second chamber, the second chamber biasing the piston against the valve seat. the piston has a predetermined size window connecting the first and second chambers;
The chamber is connected to the first chamber of the fuel spill valve and the fuel servo shutoff valve, and the second chamber is connected to the downstream high-pressure side of the low-pressure pump. upstream low pressure side, and when activated, excess fuel flow from the fuel spill valve to the downstream high pressure side of the low pressure pump flows through the first chamber, the window of the piston and the second chamber of the check valve, reducing the excess fuel flow rate. The window in the piston has a predetermined size that produces a predetermined pressure drop across the check valve when the predetermined value is reached, and the predetermined pressure drop across the check valve moves the piston in the fuel servo isolation valve. at least 1
Allows high-pressure fuel to be supplied to multiple fuel servos.

The fuel flow regulator provides high pressure fuel to the at least one fuel servo, a third chamber of a fuel servo isolation valve coupled to the at least one fuel servo, and a high pressure side of the low pressure pump, and provides at least one fuel flow from the fuel flow regulator. High pressure fuel flow to one fuel servo can be controlled.

Maintaining high-pressure fuel flow to at least one fuel servo even if excess fuel flow from the fuel spill valve to the upstream low-pressure side of the high-pressure pump drops below a predetermined value when the engine is operating at high speed. The area of the piston end remote from the second chamber of the fuel servo isolation valve is selected such that the fuel pressure on the downstream high pressure side of the low pressure pump is sufficiently high.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 4 shows a turbo fan type gas turbine engine 100, in which an air inlet 102, a fan 10
4, compressor 106, combustion system 108, turbine 11
0, an exhaust nozzle 112, and an exhaust outlet 114 in flow order. A fan duct 116 surrounds the gas generator and has an outlet 118. Combustion system 108 includes an annular combustion chamber 124 with a plurality of fuel burners 122 at an upstream end of combustion chamber 124 for supplying fuel into combustion chamber 124 . Each of the fuel burners 122 is supplied with fuel from a fuel manifold 120 . Fuel is supplied via pipe 16 from a low pressure fuel source to high pressure pump 10 which in turn passes via pipe 18 to fuel spill valve 1.
2 and the fuel flow regulator 14 with high pressure fuel. The fuel flow regulator 14 is connected to the pipe 2
0 to the fuel manifold 120 and to the fuel servo 80 via pipe 42, controller 60, and pipe 58. Excess fuel relative to burner demand is returned via pipe 40, controller 60, and pipe 26 to the low pressure upstream side of high pressure pump 10 by fuel spill valve 12. Fuel is returned from fuel servo 80 to the low pressure upstream side of high pressure pump 10 via pipe 22 or 24, controller 60, and pipe 26.

The fuel system is shown more clearly in FIGS. 1 and 2. Controller 60 includes a check valve 62 and a fuel servo shutoff valve 64. The check valve 62 includes a piston 30 that is housed in the cylinder 28 and defines two chambers 36 and 38 with the cylinder 28 .
A spring 34 is in chamber 38 to bias piston 30 against the valve seat, and chamber 38 is connected to pipe 22 and
6 is connected to pipe 40 by pipe 24. The piston 30 has a window 3 connecting the chambers 36 and 38.
2, and the size of the window 32 is chosen to produce a predetermined pressure drop. The pipe 22 is also connected by a pipe 26 to a pipe 16 on the upstream low pressure side of the high pressure pump 10. Pipe 22 is fuel servo 8
0 and conveys fuel from the fuel servo 80 to the upstream low pressure side of the high pressure pump 10.

The fuel servo cutoff valve 64 is connected to the first cylinder 44
The first cylinder 44 includes a piston 46 which is housed in the first cylinder 44 and defines two chambers 50, 52. There is a spring 48 in a chamber 50 that is connected to the pipe 22 and the chamber 52 is connected to the pipe 40. The end of the piston 46 remote from the chamber 50 is connected to the first cylinder 4
4 and through the window 55 of the second cylinder 54. Cylinder 54 defines a chamber 56 which is connected to fuel flow regulator 14 via pipe 42 and to fuel servo 80 via pipe 58.

Initially, gas turbine engine 100 is stationary. During the start-up procedure, check valve 62 and fuel servo isolation valve 64 are in the position shown in FIG. High pressure pump 10 then supplies high pressure fuel to fuel spill valve 12 and fuel flow regulator 14 . Fuel flow regulator 14 then supplies fuel manifold 120 and fuel burner 122 via pipe 20 . Fuel flow regulator 14 also supplies high pressure fuel to chamber 56 in second cylinder 54 of fuel servo isolation valve 64 via pipe 42 .

The piston 46 in the cylinder 44 of the fuel servo shut-off valve 64 is actuated by a spring in the chamber 50 to close the chamber 50.
The end of the piston 46 furthest from the piston 46 is disposed within the chamber 56 of the second cylinder 54 so that the high pressure fuel supplied from the fuel flow regulator 14 via the pipe 42 is routed via the chamber 56 and the pipe 58 to the fuel servo. 80 will not be supplied.

Any excess fuel is removed by the fuel spill valve 12 through the pipes 40, 24, the chamber 36 of the check valve 62, and the window 32.
and is returned to the low-pressure upstream side of the high-pressure pump 10 via the chamber 38 and the pipes 22, 26. Excess fuel is also supplied to the chamber 52 of the fuel servo isolation valve 64, but the pressure drop that occurs across the check valve during the start-up procedure of the gas turbine engine 100 increases the flow rate of the excess fuel and the opening of the window 32 of the piston 30. Due to its size, it is not large enough to overcome the spring 48 in the chamber 50 of the fuel servo isolation valve 64.

Once the engine starts and the capacity of the high pressure pump 10 increases, the flow of surplus fuel back upstream of the high pressure pump 10 increases. Check valve 62 is used to sense when excess fuel flow from fuel spill valve 12 has reached a sufficient amount to supply fuel servo 80. As the surplus fuel flow increases, the check valve 6
2 gradually increases due to the flow restriction by the window 32 of the piston 30. The chamber 5 of the fuel servo isolation valve 64 at any suitable condition between start-up and the lowest condition in which the fuel servo 80 requires fuel.
The window 32 has a predetermined size such that excess fuel flow across the window 32 creates a pressure drop sufficient to overcome the spring 48 in zero. Check valve 62
and fuel servo isolation valve 64 is then in the position shown in FIG. Therefore, fuel flow regulator 1
4 supplies high pressure fuel to the fuel servo via the pipe 42, the cylinder 54 of the fuel servo cutoff valve 64, and the pipe 58. Fuel from the fuel servo 80 is returned to the low pressure upstream side of the high pressure pump 10 via pipes 22 and 26.

When the surplus fuel flow rate from the fuel spill valve 12 to the low-pressure upstream side of the high-pressure pump 10 becomes extremely large,
The pressure drop across window 32 continues to increase until the pressure differential overcomes spring 34 and forces piston 30 off the valve seat. The pressure difference is thus limited and the pressure level of the entire system does not continue to increase unnecessarily.

When the engine is running at extremely high speeds, the high pressure pump 1
0 is likely operating close to maximum capacity, ie the pump capacity is very close to the fuel demand of the fuel burner. In this case, the excess fuel flow from the fuel spill valve 12 will be as low as during startup, but it is important to maintain the fuel flow to the fuel servo 80 at high engine speeds.

At very high engine speeds, the end of the piston 46 remote from the chamber 50 is connected to the fuel flow regulator 14.
A fuel servo isolation valve 64 is positioned such that it is exposed to high pressure fuel flowing from the fuel servo 80 through the pipe, chamber 56 and vape 58 to the fuel servo 80 . The pressure of high pressure fuel in chamber 56 and the area of the end of the piston remote from chamber 50 are selected to maintain piston 46 in the position shown in FIG. 2 for flowing high pressure fuel to fuel servo 80.

In the starting condition, the fuel flow regulator 1
The pressure of high pressure fuel from 4 to cylinder 54 is not sufficient to open fuel servo shutoff valve 64.

When a very small amount of surplus fuel flows from the fuel spill valve 12 to the low-pressure upstream side of the high-pressure pump 10 at a flow rate that is not sufficient to supply the surplus fuel to the fuel servo 80, the pressure drop that occurs before and after the window of the piston 30. is not large enough to overcome spring 48, check valve 62 senses that there is not enough excess fuel flow.

The fuel system of the present invention allows for proper sizing of the high pressure pump to reduce fuel circulation and temperature rise during slow engine speed conditions.

The fuel system of the present invention senses that a predetermined amount of excess fuel flow sufficient to supply the fuel servo is flowing from the fuel spill valve. If the excess fuel flow drops below a predetermined amount, such as during start-up, the supply of fuel to the fuel servo is automatically shut off by the fuel servo isolation valve. When the excess fuel flow drops to zero at high engine speeds, the high pressure fuel maintains the fuel servo isolation valve in the open position.

The embodiment of FIG. 3 is similar to that of FIGS. 1 and 2, but provides a snap action at the switching point. The check valve 62 is identical to that of FIGS. 1 and 2, and like parts are given the same numbers. The fuel servo cutoff valve 164 is built into the cylinder 144 and is connected to the three chambers 150, 1 along with the cylinder 144.
52,156. A spring 14 is located within the chamber 150 that connects to the pipe 22.
8 and the chamber 152 is connected to the pipe 40.
The end of piston 146 remote from chamber 150 is biased into chamber 156 by spring 148 . Room 1
56 is connected to the fuel flow regulator 14 through a pipe 42 and to the fuel servo 80 through a pipe 58.
connected to. Fuel servo shutoff valve 164 operates similarly to that of FIGS. 1 and 2 and will not be described repeatedly. Return fuel from the fuel servo flows into pipe 24.

The embodiment of FIG. 5 includes a fuel-cooled oil cooler 290;
A high pressure pump 210 is shown supplied with fuel from a low pressure pump 294 via a filter 292 and a pipe 216. The high pressure pump 210 is a pipe 218
High pressure fuel is supplied to the fuel spill valve 212 and fuel flow regulator 214 through the fuel spill valve 212 and the fuel flow regulator 214. Fuel flow regulator 214 provides high pressure fuel to fuel manifold 220 and also provides high pressure fuel to fuel servos 270, 272, 274 via pipe 242. Excess fuel relative to burner demand is returned to the low pressure upstream side of high pressure pump 210 by fuel spill valve 212, which is routed via pipe 240 to check valve 262 and diverter valve 282. returns excess fuel via pipes 284, 286 either upstream or downstream of the fuel cooled oil cooler 290. Fuel servo 270, 272, 274
is connected to pipe 216 via pipe 286 in this example.
and returns the fuel to the low-pressure upstream side of the high-speed pump 210.

Fuel servo 270, which is a booster stage supply valve, returns fuel directly to pipe 216 via pipes 276, 288, and 286, and fuel servo 272, 274, which drives variable stator vanes and other engine accessories, returns fuel to pipe 278 and fuel servo Return fuel through isolation valve 264 and from fuel servo 270 to pipe 28
8,286 to join the fuel flowing to pipe 216.

The fuel servo shutoff valve 264 is similar to that shown in FIGS. 2 and 3, and like parts are given the same numbers. Return pipe 240 from fuel spill valve 212 also connects to chamber 52 of fuel servo isolation valve 264 via pipe 280 and to pipe 29
8 connects the chamber 50 of the fuel servo cutoff valve 264 to a pipe 296 that supplies fuel to the low-pressure upstream side of the low-pressure pump 294. Pipe 278 is fuel servo 2
72, 274 to the chamber 56 of the fuel servo cutoff valve 264
and pipe 288 connects chamber 56 to pipe 216
Connect to.

The check valve 262 is similar to that shown in FIGS. 1-3, and the check valve piston moves in a predetermined position across the piston when excess fuel flow from the fuel spill valve is sufficient to supply the fuel servo. It has a predetermined size window to create a pressure drop. At that time,
The pressure drop is large enough to overcome the spring in the fuel servo isolation valve. The check valve and diverter valve can be arranged as a single unit rather than as two separate units as shown in FIG.

During the start-up procedure, the fuel servo isolation valve 264 is in the position shown in FIG.
90 and the high pressure pump 21 via the filter 292
0. High pressure pump 210 provides high pressure fuel to fuel flow regulator 214 and fuel spill valve 212 . Since fuel servo isolation valve 264 is closed, the majority of high pressure fuel is supplied to the fuel manifold and fuel burner via pipe 220.

The fuel returning through pipe 240 is insufficient to cause the pressure in chamber 52 to overcome the fuel pressure in chamber 50 and the spring force, causing low pressure pump 294 at low speeds.
The front-to-back pressure rise is also insufficient to overcome the fuel pressure in chamber 50 and the spring force.

The fuel servo 270 is always supplied with fuel by the fuel flow regulator;
72, 274 are supplied with fuel only when the fuel servo shutoff valve is open.

Once the engine has started, the excess fuel flow back upstream of the high pressure pump increases. As this flow rate increases, the fuel in chamber 52 increases due to the check valve, fuel pressure in chamber 50 and spring 4.
8, the piston 46 is moved and high pressure fuel flows to the fuel servos 272 and 274. At that time, the diverter valve 282 opens and directs excess fuel to the pipe 216.
can be passed to.

At very high engine speeds, the surplus fuel flow through pipe 240 is small and insufficient to keep the fuel servo shutoff valve open, but at high speeds the pressure rise across the low pressure pump is high enough to shut off the fuel pump. The valve remains open. The output from the low pressure pump 294 is applied via pipes 286, 288 to the end of the piston 46 remote from the chamber 50, which end has a small area selected to increase the force.

1-3, a fuel servo isolation valve is disposed in flow order between the high pressure pump and the fuel servo. Excess fuel from the fuel servo is returned to the low pressure side upstream of the high pressure pump. In FIG. 5, the fuel servo isolation valve is located in flow order after the high pressure pump and the fuel servo. Excess fuel from the fuel servo is returned to the upstream low pressure side of the high pressure pump via the fuel servo cutoff valve. In Figure 5, once fuel is supplied to the fuel servo, its pressure becomes low, so it is necessary to use the pressure difference before and after the low-pressure pump to keep the fuel servo shutoff valve open at high speeds. Become.

The embodiment described above allows the use of a minimum size high pressure pump.

Although the detailed description of the invention refers to a fuel servo that is supplied with high pressure fuel from a fuel flow regulator, the fuel servo may also be supplied with high pressure fuel from any point between the high pressure pump outlet and the fuel flow regulator. falling within the scope of the present invention.

[Brief explanation of the drawing]

1 is a system diagram of a fuel system of a gas turbine engine according to the invention; FIG. 2 is a system diagram of the fuel system of FIG. 1 in a second position; and FIG. 3 is an alternative embodiment of the fuel system according to the invention. FIG. 4 is a schematic diagram of a gas turbine engine having a fuel system according to the invention, and FIG. 5 is a diagram of an alternative embodiment of the fuel system according to the invention. 10...High pressure pump, 12...Fuel spill valve, 14
...Fuel flow regulator, 28...Cylinder, 30
...Piston, 32...Window, 34...Spring, 36...First
chamber, 38... second chamber, 44... first cylinder,
46... Piston, 48... Spring, 50... Second chamber,
52...First chamber, 53...Window, 54...Second cylinder, 55...Window, 56...Third chamber, 60...Control device, 62...Check valve, 64...Fuel servo cutoff valve,
144...Cylinder, 146...Piston, 148...
Spring, 150...Second chamber, 152...First chamber, 1
56...Third chamber, 164...Fuel servo cutoff valve, 2
10...High pressure pump, 212...Fuel spill valve, 21
4... Fuel flow regulator, 262... Check valve,
264... Fuel servo cutoff valve, 272, 274... Fuel servo, 294... Low pressure pump.

Claims (1)

Claims: 1. A device for supplying low pressure fuel to a high pressure pump; the high pressure pump being adapted to supply high pressure fuel to a fuel flow regulator and a fuel spill valve; the regulator is adapted to supply high pressure fuel to the at least one fuel manifold and associated fuel burner;
the fuel spill valve is adapted to return excess fuel to a low pressure side upstream of the high pressure pump; at least one fuel servo is adapted to be supplied with high pressure fuel from a location downstream of the high pressure pump; In the fuel system of a gas turbine engine: from the fuel spill valve 12 to the high pressure pump 10
The control device 60 senses the point in time when the surplus fuel flow rate to the upstream low pressure side reaches a predetermined value, and when the surplus fuel flow rate is greater than the predetermined value, the control device controls high pressure to the at least one fuel servo. A fuel system for a gas turbine engine characterized by: allowing supply of fuel. 2. The control device 60 includes a fuel servo isolation valve 64 having a piston 46 disposed within the first cylinder 44 and defining with the first cylinder 44 a first chamber 52 and a second chamber 50. ; the second chamber 50 has a spring 4 acting on the piston 46;
8 disposed inside; the end of the piston 46 remote from the second chamber 50 is located within the window 53 of the first cylinder 44 and the window 55 of the second cylinder 54.
the second cylinder defines a third chamber 56; the first chamber 52 is connected to the low pressure side of the high pressure pump 10 and the fuel spill valve 12; chamber 50 is connected to a point in the fuel system where fuel pressure is relatively low; said third chamber is adapted to control fuel flow to said at least one fuel servo; Spring 4
8 is the piston 46 farther from the second chamber
an end of the piston 46 distal from the second chamber 50 from the first position urging the end of the piston 46 into the third chamber 56 to prevent high pressure fuel flow to the at least one fuel servo; is moved out of the third chamber 56 to permit high pressure fuel flow to the at least one fuel servo; a predetermined pressure drop across the piston 46; 2. The gas according to claim 1, wherein the piston 46 is moved against the spring 48 when the pressure drop is formed and the pressure drop overcomes the spring 48. Turbine engine fuel system. 3 disposed within the cylinder 144 so that the cylinder 1
a piston 146 that, together with 44, defines a first chamber 152, a second chamber 150, and a third chamber 156;
The control device 60 includes a fuel servo isolation valve 164 having a fuel servo isolation valve 164; the second chamber 150 has a spring 148 disposed therein acting on the piston 146;
The piston 1 farther from the second chamber 150
46 is biased into the third chamber 156 by the spring 148; the first chamber 152 is connected to the low pressure side of the high pressure pump 10 and the fuel spill valve 12; the third chamber 150 is connected to a point in the fuel system where fuel pressure is relatively low; the third chamber 156 is adapted to control fuel flow to the at least one fuel servo;
a first position in which the spring 148 biases the end of the piston 146 distal from the second chamber 150 into the third chamber 156 to prevent high pressure fuel flow to the at least one fuel servo; an end of the piston 146 distal from the second chamber 150 is moved out of the third chamber 156 to a position permitting high pressure fuel flow to the at least one fuel servo;
The piston 146 is movable; a predetermined pressure drop is formed across the piston 146 such that when the predetermined pressure drop overcomes the spring 148, the piston 146 is moved against the spring 148. characterized by;
A fuel system for a gas turbine engine according to claim 1. 4 disposed within the cylinder 28 and the cylinder 28
The control device 60 includes a check valve 62 having a piston 30 defining a first chamber 36 and a second chamber 38; the second chamber 38 biasing the piston 30 against the valve seat. a spring 34 is disposed therein; the piston 30 has a predetermined size window 32 connecting the first chamber 36 and the second chamber 38; the first chamber 36 is connected to the fuel spill valve 12 and connected to the first chamber 52, 152 of the fuel servo cutoff valve 64, 164; the second chamber 3;
8 is connected to a point in the fuel system where the fuel pressure is relatively low and to the second chamber 50, 150 of the fuel servo cutoff valve 64, 164; the point where the fuel pressure in the fuel system is relatively low is connected to the high pressure upstream low pressure side of pump 10; thereby, said fuel spill valve 1
2 to the upstream low-pressure side of the high-pressure pump 10 through the first chamber 36 of the check valve 62, the window 32 of the piston 30, and the second chamber 3.
8; the window 32 of the piston 30 has a predetermined size so as to create a predetermined pressure drop across the check valve 62 when the excess fuel flow reaches a predetermined value; The predetermined pressure drop across valve 62 is determined by the fuel servo isolation valve 64;
164, wherein said piston 46, 146 in said at least one fuel servo is adapted to move said piston 46, 146 within said at least one fuel servo to permit supply of high pressure fuel to said at least one fuel servo. A fuel system for a gas turbine engine as described. 5 The fuel flow regulator 14 is connected to the third chamber 56,1 of the fuel servo cutoff valve 64,164.
5. A fuel system for a gas turbine engine according to any one of claims 2 to 4, characterized in that high pressure fuel is supplied to the at least one fuel servo via 56. 6. Move the piston 30 in the check valve 60 away from its valve seat to open the check valve 62.
The spring 34 in the second chamber 38 of the check valve 62 is selected to limit the pressure increase in the first chamber 36 of the non-return valve 62 . 4. A fuel system for a gas turbine engine according to item 4. 7. When the engine is operated at high speed, even if the surplus fuel flow from the fuel spill valve 12 to the upstream low pressure side of the high pressure pump 10 falls below the predetermined value, the pressure of the high pressure fuel may be lower than the predetermined value.
The fuel servo isolation valve 6 is of sufficient height to maintain high pressure fuel flow to the fuel servos.
Gas turbine according to claim 5, characterized in that the area of the end of the piston 46, 146 remote from the second chamber 50, 150 of 4,164 is selected. Engine fuel system. 8 disposed within the cylinder 28 and the cylinder 28
The control device 60 includes a check valve 262 having a piston 30 defining a first chamber 36 and a second chamber 38; the second chamber 38 biasing the piston 30 against the valve seat. With a spring 34 disposed therein, the piston 30 has a window 32 of a predetermined size connecting the first chamber 36 and the second chamber 38; the first chamber 36 is connected to the fuel spill valve 212 and the The first chamber 52 of the fuel servo cutoff valve 264
the second chamber 38 is connected to a relatively low fuel pressure point in the fuel system and the fuel servo cutoff valve 2;
64; a portion where the fuel pressure of the fuel system is relatively low is connected to the low pressure pump 29;
4; whereby excess fuel flow from the fuel spill valve 212 to the downstream high pressure side of the low pressure pump 294 is directed to the first chamber 36 of the check valve 262, the window 32 of the piston 30 and Second
window 32 in the piston 30 has a predetermined size so as to create a predetermined pressure drop across the check valve 262 when excess fuel flow reaches a predetermined value; The predetermined pressure drop across the stop valve 262 is equal to the predetermined pressure drop across the stop valve 262.
3. The gas pump according to claim 2 or 3, wherein the piston 46 within the gas servo is adapted to move to allow supply of high pressure fuel to the at least one fuel servo. Turbine engine fuel system. 9 the fuel flow regulator 214 supplies high pressure fuel to the at least one fuel servo 272, 274;
The third chamber 56 of the fuel servo isolation valve 264 connects the at least one fuel servo 272, 274 and the low pressure side of the high pressure pump 210 to control high pressure fuel flow to the high pressure pump 210. thing;
A fuel system for a gas turbine engine according to claim 2, 3, or 8, characterized by: 10 Even if the surplus fuel flow rate from the fuel spill valve 212 to the upstream low-pressure side of the high-pressure pump 210 drops below the predetermined value during high-speed engine operation, the fuel pressure on the downstream high-pressure side of the low-pressure pump 294 of the piston 46 distal to the second chamber 50 of the fuel servo isolation valve 264 such that 10. Fuel system for a gas turbine engine according to claim 9, characterized in that the end areas are selected.